Conventional thrust reversers for aircraft gas turbine engines are provided for deflecting exhaust gases discharged from the engine in a generally forward direction upon landing of an aircraft for assisting in braking the aircraft. The thrust reverser is typically designed to translate from a stowed position, wherein it is aerodynamically blended with a conventional nacelle surrounding the engine, to a deployed position spaced rearwardly of the engine exhaust nozzle so that the exhaust gases are turned forwardly while avoiding back pressure in the exhaust gases which would affect performance of the engine.
Target-type thrust reversers for underwing or fuselage mounted engines typically include a pair of symmetrical deflector doors, or deflectors, for providing thrust reversal. In an overwing mounted gas turbine engine, conventional thrust reversers are typically unsymmetrical and must function within a relatively confined area between the engine and the wing. There are several types of conventional target-type overwing thrust reversers which utilize one or more deflectors and various actuators, linkages, and cam slots for positioning the deflectors between stowed and deployed positions.
The required travel of the deflector between the stowed and deployed positions is typically relatively large, thus requiring suitable actuators and linkages. The actuators and linkages must be suitably coordinated for ensuring effective deployment of the deflector without undesirable cocking thereof. Thrust reversers utilizing such actuators and linkages are sometimes referred to as semi-floating thrust reversers since the deflector is supported, translated and rotated at several joints. Such a thrust reverser is relatively complex and subject to wear at the various joints.
Conventional thrust reversers also utilize at least two deflector doors for obtaining thrust reversal in order to obtain a relatively large change in direction of the exhaust gas flow with relatively short actuator strokes and rotation of the individual doors, for example. Such multidoor thrust reversers add to the complexity of the thrust reverser assembly and, therefore, are generally less desirable.
Conventional overwing thrust reversers also include actuation mechanisms which are disposed either adjacent to the wing outer surface, or within the aircraft wing itself, or both, which is generally undesirable for serviceability and since the aircraft wing is designed primarily for other conventional purposes. In overwing thrust reversers, there is generally little available space between the exhaust nozzle and the wing in which to mount the actuator mechanisms which thus affects the ability to obtain efficient discharge of the exhaust gases from the exhaust nozzle.
Furthermore, in operation, the thrust reverser is typically deployed when an aircraft is landing and is rolling at relatively high speed. Therefore, it is subject to relatively high air velocity passing over the engine and wing which generates substantial aerodynamic pressure forces on the deflector which must be suitably accommodated for minimizing or preventing buffeting of the deflector during deployment. The forces due to the airflow over the engine during landing are in addition to the forces generated by the exhaust gases discharged from the engine exhaust nozzle against the deflector for thrust reversal, which must also be accommodated by the linkages attaching the deflector to the engine, nacelle, and/or wing. Such considerably large aerodynamic forces against the deflector generate substantial reaction loads in the actuation mechanism as well as generating reaction loads in the deflector. The deflector and actuation mechanisms must, therefore, be substantially rigid for accommodating these reaction loads without undesirable distortion of the deflector or of the actuation mechanisms.